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Slow-moving meteors during February are a well-known phenomenon but astronomers are mystified as to where they come from.

Fri Feb 24, 2012 07:00 AM ET
Content provided by SPACE.com Staff

THE GIST

The strange deep-diving, slow-moving fireballs started falling on Feb. 1.

They range in size from basketballs to buses and some are thought to have dropped meteorites.

Astronomers know the objects originate in the asteroid belt, but little else is known.

A fireball over north Georgia recorded on Feb. 13 by a NASA all-sky camera in Walker County, Georgia.NASA

A strange breed of fireball is streaking through the skies this month, and NASA is urging folks on the ground to take notice.

February’s fireballs — a term that describes meteors that appear brighter in the sky than Venus — aren’t more numerous than normal, but their appearance and trajectory are odd, experts say.

“These fireballs are particularly slow and penetrating,” meteor expert Peter Brown, a physics professor at the University of Western Ontario, said in a statement. “They hit the top of the atmosphere moving slower than 15 kilometers per second (33,500 mph), decelerate rapidly and make it to within 50 kilometers (31 miles) of Earth’s surface.”

Beginning February With a Bang

The month’s fireball action began on Feb. 1, when a meteor lit up the skies over central Texas, putting on a dazzling show for people in the Dallas-Fort Worth area.

“It was brighter and long-lasting than anything I’ve seen before,” said eyewitness Daryn Morran. “The fireball took about eight seconds to cross the sky. I could see the fireball start to slow down; then it exploded like a firecracker artillery shell into several pieces, flickered a few more times and then slowly burned out.”

The fireball was about as bright as the full moon, and was spotted by NASA cameras in New Mexico, more than 500 miles (805 km) away. It was likely caused by an object 3 to 6 feet (1 to 2 meters) wide, NASA researchers said.

And the meteors have kept coming, well into February.

“This month, some big space rocks have been hitting Earth’s atmosphere,” said Bill Cooke of the Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. “There have been five or six notable fireballs that might have dropped meteorites around the United States.”

Oddball Fireballs

So far in February, NASA’s All-Sky Fireball Network — which currently consists of six cameras set up in Georgia, Alabama, Tennessee and New Mexico — has photographed about half a dozen of these strange slow-moving, deep-diving fireballs. They have ranged in size from basketballs to buses.

Cooke has analyzed their orbits and determined where the strange meteors are coming from.

“They all hail from the asteroid belt, but not from a single location in the asteroid belt,” he said. “There is no common source for these fireballs, which is puzzling.”

The “fireballs of February” have puzzled astronomers for decades. Skywatchers first noticed an increase in the number of deep-penetrating, bright meteors during February back in the 1960s and ’70s, Brown said.

Research to date has been inconclusive, with some studies reporting a surge of these fireballs in February and others detecting no such trend, Brown added.

But NASA’s All-Sky Fireball Network could end up solving the mystery. Cooke and his colleagues plan to keep adding cameras to the network, increasing its coverage across North America.

“The beauty of our smart multi-camera system,” Cooke said, “is that it measures orbits almost instantly. We know right away when a fireball flurry is underway — and we can tell where the meteoroids came from.”

While Cooke and other researchers ponder the origins of February’s fireballs, the rest of us still have a few days left to enjoy them this year.

“If the cows and dogs start raising a ruckus tonight,” Cooke said, “go out and take a look.”

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Calm as a mill pond: The normally steady waters around St Michael’s Mount, Cornwall, were hit by the unexpected mini-tsunami

This week, parts of the Cornish coastline were hit by what appears to have been a mini-tsunami. The wave was of no great height, but it was still substantial enough to suck the sea out for 150 feet or more, before surging back in to drench the causeway linking St Michael’s Mount to the mainland near Penzance, and giving tourists a soaking.

The wave rolled up the estuaries and rivers from Mounts Bay in the West to Plymouth in the east, sending small boats rolling on their keels.

If that isn’t strange enough, witnesses said it was preceded by a surge of static electricity. ‘People’s hair stood on end,’ said a National Trust guide on the Mount.

Others reported the air going unnaturally still, with a dense, warm clamminess settling over land and sea before the wave struck.

Of course, the Cornish tsunami on Monday morning was tiny compared to the one that devastated Japan earlier this year. But the reports raise a tantalising question; might we have found one of the great holy grails of seismology — a reliable way of predicting earthquakes which could save thousands of lives?

Experts suggest that the Cornish tsunami was caused by either a small earthquake or an undersea landslide off the Irish coast 250 miles away.

One theory is that the resulting rock vibrations could generate a powerful electrical charge, strong enough to travel all the way along the seabed to land, up the beach, and reach the top of a tourist’s head.

‘It’s called the Piezoelectric Effect,’ says Chris Shepherd of the Institute of Physics, explaining that quartz crystals, present in the ancient rocks in and around Cornwall, could generate a high voltage if squeezed. ‘It’s the same effect used in gas lighters on your cooker.’

Intriguingly, something similar but far more dramatic seems to have taken place several days before the Japanese earthquake.

After studying data sent by satellites over the Pacific Ocean, NASA scientists at the Goddard Space Flight Centre in Maryland have discovered that there was a sudden and dramatic pulse of heat high in the atmosphere over the epicentre of the quake 72 hours before it struck.

The heat pulse was associated with an equally dramatic increase in electrical charge in the air. Similar effects were reported, retrospectively, before the Haiti earthquake in 2007.

Just what was happening is something of a mystery. A persistent conspiracy theory doing the rounds on the internet links recent big earthquakes and secret radio experiments allegedly being carried out by the Pentagon.

Far more likely, however, is a little-understood phenomenon called the ‘Lithosphere-Atmosphere-Ionosphere Coupling mechanism’.

The theory is that in the days before an earthquake, the great stresses that have built up cause the release of large amounts of radioactive radon gas from deep in the Earth.

The radioactivity from this gas ionises the air on a large scale, electrifying it and heating it up. So could something like this, on a smaller scale, have explained the weird phenomena seen in Cornwall this week?

Perhaps what we saw was a combination of the piezoelectric effect and the release of radon gas — large quantities of which are present in Cornish rocks.

It is still very much a mystery. Dr Simon Boxall, an oceanographer who was out at sea on a small boat off the coast of Falmouth when the tsunami struck, thinks the wave had nothing to do with an earthquake at all, but instead was something called a ‘seiche’.

‘I’m 99 per cent certain,’ he says, pointing out that seismographs of the British Geological Survey did not seem to have detected any earth-shaking at all before the wave struck.

A seiche is a freak wave which can be caused by an area of very low or high pressure crossing an area of water.

If the speed at which the weather system is moving is just right, the sea underneath can ‘resonate’ like a wine glass ringing when you rub the rim in the right way, and a single big wave can come seemingly from nowhere.

‘The static had nothing directly to do with the wave, but it did have a lot to do with the low-pressure system,’ Dr Boxall insists, adding that southern England was hit by a number of powerful thunderstorms later that day.

‘The air would have been charged with static.’

Whatever the explanation, we may be getting tantalisingly close to finding a way to predict earthquakes — something dismissed as a pseudoscience until very recently.

For centuries there have been reports of lightning, static and even fireballs in the sky associated with earthquakes together with, of course, persistent reports that animals are able to sense that something is about to happen and flee to higher ground.

These reports are now being taken more seriously.

More than a third of a million people perished in the Indian Ocean tsunami, and 25,000 more in Japan this year.

If satellites — or even the hairs on the back of your neck — could be used to predict disasters like these hours or even days ahead, millions of lives could be saved in years to come.

CONGESTED INTERSECTION: Ranging in size from microscopic space dust to mountainous asteroids, trillions of meteoroids zing through the inner solar system on a daily basis. What are the odds that five of them would cross the same point in space? Pretty good, actually. In fact, it happened just last night. Regard the following orbit diagram, then read on for an expanation:

These are the orbits of five objects that hit Earth on the night of Dec. 7/8. NASA’s All Sky Fireball Network recorded the meteoroids as they disintegrated in the atmosphere over the United States, each one producing a bright fireball. Note how all the orbits converge on a single point–our planet.

Every night the network’s cameras scan the skies over the United States, forming an inventory of what hits the atmosphere. Combining images from multiple cameras, network software rapidly calculates the basic parameters of each interloper: orbit, speed, disintegration height, and more. At the moment, cameras are located in only four states (New Mexico, Alabama, Georgia, Tennessee), but the network is expanding to provide even better coverage. Soon we’ll see just how congested our intersection in space really is. Stay tuned.